/*
 * Copyright 2002-2018 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.web.server.adapter;

import java.util.Arrays;
import java.util.HashSet;
import java.util.Set;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import reactor.core.publisher.Mono;

import org.springframework.context.ApplicationContext;
import org.springframework.core.NestedExceptionUtils;
import org.springframework.http.HttpStatus;
import org.springframework.http.codec.ServerCodecConfigurer;
import org.springframework.http.server.reactive.HttpHandler;
import org.springframework.http.server.reactive.ServerHttpRequest;
import org.springframework.http.server.reactive.ServerHttpResponse;
import org.springframework.lang.Nullable;
import org.springframework.util.Assert;
import org.springframework.web.server.ServerWebExchange;
import org.springframework.web.server.WebHandler;
import org.springframework.web.server.handler.WebHandlerDecorator;
import org.springframework.web.server.i18n.AcceptHeaderLocaleContextResolver;
import org.springframework.web.server.i18n.LocaleContextResolver;
import org.springframework.web.server.session.DefaultWebSessionManager;
import org.springframework.web.server.session.WebSessionManager;

/**
 * Default adapter of {@link WebHandler} to the {@link HttpHandler} contract.
 *
 * <p>By default creates and configures a {@link DefaultServerWebExchange} and
 * then invokes the target {@code WebHandler}.
 *
 * @author Rossen Stoyanchev
 * @author Sebastien Deleuze
 * @since 5.0
 */
public class HttpWebHandlerAdapter extends WebHandlerDecorator implements HttpHandler {

    /**
     * Dedicated log category for disconnected client exceptions.
     * <p>Servlet containers do not expose a notification when a client disconnects,
     * e.g. <a href="https://java.net/jira/browse/SERVLET_SPEC-44">SERVLET_SPEC-44</a>.
     * <p>To avoid filling logs with unnecessary stack traces, we make an
     * effort to identify such network failures on a per-server basis, and then
     * log under a separate log category a simple one-line message at DEBUG level
     * or a full stack trace only at TRACE level.
     */
    private static final String DISCONNECTED_CLIENT_LOG_CATEGORY =
            "org.springframework.web.server.DisconnectedClient";

    /**
     * Tomcat: ClientAbortException or EOFException
     * Jetty: EofException
     * WildFly, GlassFish: java.io.IOException "Broken pipe" (already covered)
     * <p>TODO:
     * This definition is currently duplicated between HttpWebHandlerAdapter
     * and AbstractSockJsSession. It is a candidate for a common utility class.
     *
     * @see #isDisconnectedClientError(Throwable)
     */
    private static final Set<String> DISCONNECTED_CLIENT_EXCEPTIONS =
            new HashSet<>(Arrays.asList("ClientAbortException", "EOFException", "EofException"));


    private static final Log logger = LogFactory.getLog(HttpWebHandlerAdapter.class);

    private static final Log disconnectedClientLogger = LogFactory.getLog(DISCONNECTED_CLIENT_LOG_CATEGORY);


    private WebSessionManager sessionManager = new DefaultWebSessionManager();

    @Nullable
    private ServerCodecConfigurer codecConfigurer;

    @Nullable
    private LocaleContextResolver localeContextResolver;

    @Nullable
    private ApplicationContext applicationContext;


    public HttpWebHandlerAdapter(WebHandler delegate) {
        super(delegate);
    }

    /**
     * Return the configured {@link WebSessionManager}.
     */
    public WebSessionManager getSessionManager() {
        return this.sessionManager;
    }

    /**
     * Configure a custom {@link WebSessionManager} to use for managing web
     * sessions. The provided instance is set on each created
     * {@link DefaultServerWebExchange}.
     * <p>By default this is set to {@link DefaultWebSessionManager}.
     *
     * @param sessionManager the session manager to use
     */
    public void setSessionManager(WebSessionManager sessionManager) {
        Assert.notNull(sessionManager, "WebSessionManager must not be null");
        this.sessionManager = sessionManager;
    }

    /**
     * Return the configured {@link ServerCodecConfigurer}.
     */
    public ServerCodecConfigurer getCodecConfigurer() {
        return (this.codecConfigurer != null ? this.codecConfigurer : ServerCodecConfigurer.create());
    }

    /**
     * Configure a custom {@link ServerCodecConfigurer}. The provided instance is set on
     * each created {@link DefaultServerWebExchange}.
     * <p>By default this is set to {@link ServerCodecConfigurer#create()}.
     *
     * @param codecConfigurer the codec configurer to use
     */
    public void setCodecConfigurer(ServerCodecConfigurer codecConfigurer) {
        Assert.notNull(codecConfigurer, "ServerCodecConfigurer must not be null");
        this.codecConfigurer = codecConfigurer;
    }

    /**
     * Return the configured {@link LocaleContextResolver}.
     */
    public LocaleContextResolver getLocaleContextResolver() {
        return (this.localeContextResolver != null ?
                this.localeContextResolver : new AcceptHeaderLocaleContextResolver());
    }

    /**
     * Configure a custom {@link LocaleContextResolver}. The provided instance is set on
     * each created {@link DefaultServerWebExchange}.
     * <p>By default this is set to
     * {@link org.springframework.web.server.i18n.AcceptHeaderLocaleContextResolver}.
     *
     * @param localeContextResolver the locale context resolver to use
     */
    public void setLocaleContextResolver(LocaleContextResolver localeContextResolver) {
        this.localeContextResolver = localeContextResolver;
    }

    /**
     * Return the configured {@code ApplicationContext}, if any.
     *
     * @since 5.0.3
     */
    @Nullable
    public ApplicationContext getApplicationContext() {
        return this.applicationContext;
    }

    /**
     * Configure the {@code ApplicationContext} associated with the web application,
     * if it was initialized with one via
     * {@link org.springframework.web.server.adapter.WebHttpHandlerBuilder#applicationContext
     * WebHttpHandlerBuilder#applicationContext}.
     *
     * @param applicationContext the context
     * @since 5.0.3
     */
    public void setApplicationContext(ApplicationContext applicationContext) {
        this.applicationContext = applicationContext;
    }

    @Override
    public Mono<Void> handle(ServerHttpRequest request, ServerHttpResponse response) {
        ServerWebExchange exchange = createExchange(request, response);
        return getDelegate().handle(exchange)
                .onErrorResume(ex -> handleFailure(request, response, ex))
                .then(Mono.defer(response::setComplete));
    }

    protected ServerWebExchange createExchange(ServerHttpRequest request, ServerHttpResponse response) {
        return new DefaultServerWebExchange(request, response, this.sessionManager,
                getCodecConfigurer(), getLocaleContextResolver(), this.applicationContext);
    }

    private Mono<Void> handleFailure(ServerHttpRequest request, ServerHttpResponse response, Throwable ex) {
        if (isDisconnectedClientError(ex)) {
            if (disconnectedClientLogger.isTraceEnabled()) {
                disconnectedClientLogger.trace("Looks like the client has gone away", ex);
            } else if (disconnectedClientLogger.isDebugEnabled()) {
                disconnectedClientLogger.debug("Looks like the client has gone away: " + ex +
                        " (For a full stack trace, set the log category '" + DISCONNECTED_CLIENT_LOG_CATEGORY +
                        "' to TRACE level.)");
            }
            return Mono.empty();
        }
        if (response.setStatusCode(HttpStatus.INTERNAL_SERVER_ERROR)) {
            logger.error("Failed to handle request [" + request.getMethod() + " "
                    + request.getURI() + "]", ex);
            return Mono.empty();
        }
        // After the response is committed, propagate errors to the server..
        HttpStatus status = response.getStatusCode();
        logger.error("Unhandled failure: " + ex.getMessage() + ", response already set (status=" + status + ")");
        return Mono.error(ex);
    }

    private boolean isDisconnectedClientError(Throwable ex) {
        String message = NestedExceptionUtils.getMostSpecificCause(ex).getMessage();
        message = (message != null ? message.toLowerCase() : "");
        String className = ex.getClass().getSimpleName();
        return (message.contains("broken pipe") || DISCONNECTED_CLIENT_EXCEPTIONS.contains(className));
    }

}
